Many conventional Optical Character Recognition (OCR) methods require that text be orientated right side up to be accurately read. However, numerous practical applications involve documents of unknown orientation; for example, as mail is collected in a mail collection box, the right side up orientation cannot be guaranteed. Similarly, when documents are scanned, photocopied, or received via facsimile, the orientation could be right side up or upside down, or sideways, or on an angle.
To address practical concerns such as these, a number of solutions have been put forth. For instance, optical character recognition may be performed in both directions (i.e., right side up and upside down) on a document, and the two (OCR) confidences may be used as indications as to whether the document is upside down or right side up. Alternatively, watermarks or magnetic ink may be used to mark a document in a way that facilitates a determination of orientation. A third solution relies on the fact that, statistically, English text comprises more “ascenders” (e.g., letters such as a lowercase b, d, or h, that have character strokes extending above a base line of text) than “descenders” (e.g., letters such as a lowercase p, q or j, that have character strokes extending below a base line of text). Thus, it is assumed that a document in which a greater number of characters have strokes extending above base lines of text, as opposed to below the base lines, is orientated right side up.
While such solutions have generally proven to be successful, their utility is limited to a very small number of situations. Those methods that are not computationally expensive or slow typically do assume prior knowledge of special formats, or will not work for documents that (a) comprise characters that are all capital letters (e.g., addresses, tax forms); (b) are written in italics; or (c) are printed in another language or alphabet.
Thus, there is a need in the art for a method and apparatus for determination of text orientation that is economical and efficient, and is capable of use in a variety of formats.